// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_SEQUENCE_CHECKER_IMPL_H_
#define BASE_SEQUENCE_CHECKER_IMPL_H_

#include "base/base_export.h"
#include "base/compiler_specific.h"
#include "base/macros.h"
#include "base/sequence_token.h"
#include "base/synchronization/lock.h"
#include "base/threading/sequenced_worker_pool.h"
#include "base/threading/thread_checker_impl.h"

namespace base {

// Real implementation of SequenceChecker for use in debug mode or for temporary
// use in release mode (e.g. to CHECK on a threading issue seen only in the
// wild).
//
// Note: You should almost always use the SequenceChecker class to get the right
// version for your build configuration.
class BASE_EXPORT SequenceCheckerImpl {
public:
    SequenceCheckerImpl();
    ~SequenceCheckerImpl();

    // Returns true if called in sequence with previous calls to this method and
    // the constructor.
    bool CalledOnValidSequence() const WARN_UNUSED_RESULT;

    // Unbinds the checker from the currently associated sequence. The checker
    // will be re-bound on the next call to CalledOnValidSequence().
    void DetachFromSequence();

private:
    void EnsureSequenceTokenAssigned() const;

    // Guards all variables below.
    mutable Lock lock_;

    // True when the SequenceChecker is bound to a sequence or a thread.
    mutable bool is_assigned_ = false;

    mutable SequenceToken sequence_token_;

    // TODO(gab): Remove this when SequencedWorkerPool is deprecated in favor of
    // TaskScheduler. crbug.com/622400
    mutable SequencedWorkerPool::SequenceToken sequenced_worker_pool_token_;

    // Used when |sequenced_worker_pool_token_| and |sequence_token_| are invalid.
    ThreadCheckerImpl thread_checker_;

    DISALLOW_COPY_AND_ASSIGN(SequenceCheckerImpl);
};

} // namespace base

#endif // BASE_SEQUENCE_CHECKER_IMPL_H_
